1. Field of the Invention
The invention relates to a system for controlling the shape of a strip metal which is being manufactured.
2. Prior Art
The shape of a strip of metal is defined in the art as the cross-directional stress profiled of the sheet while the sheet is under tension. During production of a strip of metal, and particularly during the rolling process, the shape of the strip can be changed. It is important that after production the shape of the strip is as nearly perfectly flat as possible, i.e. minimal cross-directional variations in stress. Various methods are known for accomplishing this.
U.S. Pat. No. 4,262,511 teaches a system for controlling the shape of sheet metal. According to the patent a metal sheet is compressed between a pair of driven shaping rolls, or work rolls. The sheet is measured by a shapemeter, and deviations from a predetermined target shape are corrected. One of the methods of correction is to spray cooling liquid onto the work rolls in the area in which the rolls are determined to be applying excessive force to the sheet. Thus the rolls are cooled so that they contract and consequently apply less force.
According to the patent, an incremental increase or decrease in coolant spray is applied as long as the shape, as measured by the shapemeter, is outside specified limits. Then, when the shape is within limits, the sprays are returned to their normal level.
It has been found that controlling the sprays in the manner taught in the patent can lead to the production of sheet in which the shape is not well controlled and cannot effectively control foil producing rolling mills. Sheet is defined as strip which is greater in thickness than 0.006 inch, and foil is a strip of less than 0.006 inch thickness.